Binding and internalization of lysosomal enzymes by primary cultures of rat glia

✍ Scribed by D. F. Hill; P. N. Bullock; F. Chiappelli; L. H. Rome

• Book ID: 102910601
• Publisher: John Wiley and Sons
• Year: 1985
• Tongue: English
• Weight: 821 KB
• Volume: 14
• Category: Article
• ISSN: 0360-4012
• DOI: 10.1002/jnr.490140104

✦ Synopsis

Highly purified cultures of rat astrocytes and oligodendrocytes were examined for their ability to bind and internalize lysosomal enzymes. Astrocytes displayed a saturable uptake of 0-glucosidase and /3-galactosidase. The uptake was specifically inhibited by mannose-6-phosphate but not by several other sugars or sugar phosphates, indicating that the process was mediated by mannose-6-phosphate receptors. When cells were allowed to take up '2sI-/3-glucosidase for 1 hr at 37°C and subcellular organelles were isolated, the enzyme was shown to comigrate with a lysosomal organelle marker enzyme, suggesting that the enzyme was targeted to lysosomes. Astrocyte receptors were probed directly by binding of Iz5I labeled 0glucosidase to astrocyte membranes at 4°C. Binding was saturable and competitively inhibited by mannose-6-phosphate. In contrast to the astrocytes, cultured oligodendrocytes showed no specific binding or uptake of the lysosomal enzymes. Immunocytochemical staining of mixed glial cultures supported the biochemical data; only the astrocytes stained positive with anti-mannose-6-phosphate receptor antibodies.